Hi Iacdxb,
The simplest way to see the effect of the intermediate points, is given with the Circle Spline Primitive. Call one up and while it is active, go to the Attribute Manager and set under Object the Angle to 90º. Now it is a square.
Why is that? The Circle is described as Primitive only by four points, anything else is based on intermediate points, which are points set by the application based on the rules are given to them. In the case above, if the direction change is create/equal to 90º, a new point would have been set (internally), but the four points inside the default (MAXON) definition is already sufficient for the 90º rule, hence the square.
These intermedia points are not visible or selectable in the Spline itself. If you make the Spline “editable”, you will have acces to those, but then the option to adjust them in the Attribute Manager is gone.
There is an option to have None, Natural, Uniform, Adaptive and Subdivided. The rules are simple, if a certain change would be in the spline, the intermedia point will be set, and this describes the degree option., which is the case in Subdivided and Adaptive. Then there is a certain distance, e.g., in the Subdivided option, what ever comes first will set a point. Natural and Uniform use a fixed number of intermediate points, but with a different set of rules. Of course there is None, which leaves only the visible points given.
Place a any Primitive-Spline or Spline object under an Extrude [NURBS] with and a “Movement” of Z = 200, and set the Display mode to anything with Lines if you like. Now adjust the Intermediate points and have a look how they change the result. I have attached an example, which I have animated, just to visualize it.
These points are more than often responsible for the results, but MoGraph (see example) use here only the default definition, not the intermediate points.
The Help Content has a written Tutorial. I have discussed this theme back in time with R8 - but I can’t find them either. There was nearly no change in the last decade, except that the Subdivided was added at one point.
I hope the example will shed some light on it. Especially with the Sweep [NURBS] these adjustments are very important.
Let me know if there is another question. I do not like to just copy and paste the Help Menu here, as you have it with a CTRL/CMD or right mouse click on the parameter instantly.
All the best
Sassi
Images [left] Help Menu Content, [right] attached scene file.